During anaphase, the spatial position of the centromere with respect to the chromosome arms becomes obvious when imaged with the microscope. Because the sister chromatids are drawn towards the spindle poles by microtubules attached to the centromere, the arms appear to be trailing behind. Morphologically, the chromosomes can be divided into three classes. Metacentric chromosomes have the centromere located at or near the middle of the structure, resulting in two arms of equivalent (or nearly so) length. These chromosomes appear V-shaped when observed during anaphase. In contrast, a telocentric chromosome has the centromere positioned very near one end and appears to migrate as a single arm. A majority of the chromosomes, however, are acrocentric, with the centromere positioned somewhere between the center and the end of the chromatid to yield an L-shaped structure in the microscope.